This is No. 21 departing Winona Jct. The three forward domes are CZ cars. During the mid-1950s, Burlington frequently pulled the trio of domes (chair cars) from a CZ consist for use on the Twins (either 21-24's or 22-23's consist, but not both trains simultaneously;
21-24 seems to have been the more-frequent of the two) as circumstances dictated - together with pre-war general-service chair cars. This appears to have been a weekend phenomenon and was likely exacerbated by the ascendancy of the "Creative Traffic" program
which included one-day round-trip tours from Chicago and the Twin Cities to East Dubuque and Prairie du Chien; by the late 1950s, TCZ mid-week consists were usually six cars. Earliest and latest confirmed dates are December 1953 and August 1958 (the photo
at the bottom of p. 58 in Bulletin 57 depicts the latter). The addition of a pattern dome could result in nine domes (eight chair-car; one parlor car) in one train, the most ever operated by any carrier in one stand-alone (as opposed to consolidated) train.
This required that the three domes (chair cars) arriving Chicago on No. 18 return west that same afternoon on No. 17, something that looked better on paper than in actual practice. It was difficult enough when 18 was on-time, and frequently resulted in grievously-late
departures (as late as 6 or 7 p.m.) of No. 17 when 18 was late. I rather suspect that following one-too-many late origin-terminal departures of No. 17, Messrs. Aydelott and Whitman had enough and collectively lowered the boom on Harry Murphy, ending the practice.
The train in the Winona Jct. photo has a "downstairs" capacity of 508 in the chair cars and an additional 168 in the seven chair-car domes. The dome seats weren't to be counted as revenue seats, but were used as such when the need arose, so that this train
has the potential of having in excess of 600 chair-car passengers aboard. (In such circumstances, the two guys assigned to 21-24's baggage-buffet probably qualified as the hardest-working employees on the Burlington.) Its worth noting that a second dining
car (also pulled from the CZ) wasn't used; the diner arriving Chicago on 18 couldn't be turned back the same day on No. 17 (due to the amount of cleaning, inspection, servicing, and restocking and the time that all of that required) and all of the other lightweight
dining cars were in assigned service, so the one car sufficed.
At the risk of making too fine a point, in all of the internal CB&Q/C&S/FW&D correspondence I've reviewed, "amplify" and "amplified" were terms associated with adding conventional streamlined cars to the fixed-consist articulated/semi-articulated trainsets
but weren't used when additional cars were added to the consists of non-articulated trains.
Bill